1. Field of the Invention
This invention is directed to electrodes used in electrosurgical procedures.
2. Description of Related Art
Numerous patents and patent applications exist in the field of electrosurgical methods and apparatuses that describe electrode shapes used to modify tissue in vivo. Early devices, including the design of their electrodes, were crude, and advances in surgical techniques over the years, especially the development of surgery using endoscopes (arthroscopic surgery), have continually led to new designs of electrodes as new uses call for the design of an apparatus specifically designed for that new use. Arthroscopic surgery is becoming increasingly popular, because it generally does less damage than open procedures, produces less scarring in and around joints, and results in faster healing and return of the patient to full productivity.
Nevertheless, arthroscopic surgery has its limitations. The surgeon must operate through a narrow tube formed in the body on which surgery is being carried out, which is awkward. Only one probe can be used at a time for many operations. Often the viewing camera is positioned at an angle different from the surgeon""s normal gaze. This contrasts with xe2x80x9copen surgeryxe2x80x9d where the surgeon has relative ease of viewing the surgical site and can freely move both hands, even utilizing the hands of colleagues.
In view of such difficulties of arthroscopic surgery, it is understandable that radiofrequency (RF) probes which simultaneously cut and coagulate are preferred. However, current RF probes are poorly adapted to certain activities, such as smoothing surfaces located at an angle to the axis of entry of an arthroscopic probe.
Current probes have convex, pointed and/or flat tips and are generally oriented so that the ablation process occurs substantially along the axis of the elongated probe being used for the operation. U.S. Pat. No. 5,308,311 (issued May 3, 1994 to Eggers and Shaw) is exemplary in that it has a pointed tip with a convex side. With current probes, the surgeon has poor ability to ablate tissue in directions off the axis of insertion of the probe and little control when attempting to ablate a tough substrate, such as cartilage. Thus, there are certain procedures that surgeons still prefer to perform in the xe2x80x9copen.xe2x80x9d Unfortunately, this often results in bigger scars, longer convalescence, and more irritation of an already irritated joint.
What is needed is a probe that can direct ablation of tissue at an angle to the principal axis of the probe, as well as a technique for easy manufacture of such an apparatus. Some procedures which have been considered too awkward or difficult to perform by arthroscopy can then be performed efficiently by arthroscopy.
It is an object of the invention to provide an electrode for an electrosurgical apparatus capable of superior performance in ablating collagen, including collagen present in cartilage, relative to existing electrodes.
It is a further object of the invention to provide an electrode for an electrosurgical apparatus that can ablate tissue at an angle to the principal axis of the probe on which it is used without requiring a bend in the probe itself.
It is another object of the invention to provide an electrode for an electrosurgical apparatus that can be adapted to multiple end uses by a single selection of a mechanical operation on different locations on the electrode surface during manufacture of the electrode.
These and other objects of the invention as will hereinafter become more readily apparent have been accomplished by providing an electrosurgical electrode, comprising a metal conductor having a first external surface area and having a convex body, a flat face on the body, and a connector for attaching the body to an electrosurgical probe handle, and an insulating layer covering the first external surface of the metal conductor except at a selected second area of one of the convex body and the flat face, the second area being positioned on the metal conductor so that a line from a geometric center of the second area and substantially perpendicular to the second area intersects at an angle an axis formed by a probe handle and the metal conductor upon attachment of a probe handle to the connector, wherein the second area is less than 30% of the first area.
The electrode is used in preferred embodiments in an electrosurgical probe, comprising a handle, an elongated probe neck connected to the handle and having a terminus distal to the handle, and the electrode of the invention located at the terminus of the elongated probe neck. The electrosurgical probe so formed is preferably used as part of an electrosurgical system, comprising an electrical power supply, a first electrode adapted to contact and electrically ground a living body, the first electrode being electrically connected to the power supply, and an electrosurgical probe, the probe comprising a handle, an elongated probe neck connected to the handle and having a terminus at a distal end from the handle, and a second electrode, the second electrode being the electrode of the invention and being located at the terminus of the elongated probe neck, the probe being adapted to contact the body and complete an electrical circuit, the second electrode being electrically connected to the power supply.
Also provided is a general method of manufacturing off-axis electrosurgical electrodes, by preparing a metal conductor having a first external surface area and having a first body shape and a connector for attaching the body to an electrosurgical probe handle, applying an insulating layer to cover all of the first external surface of the metal conductor, and removing a portion of the insulating layer at a selected second area of the body shape, the second area being positioned on the metal conductor so that a line from a geometric center of the second area and substantially perpendicular to the second area intersects the principal axis of the probe at an angle, the axis being defined by the probe handle and the metal conductor upon attachment of a probe handle to the connector, generally through an elongated linear neck. Any electrode so formed is also part of the present invention.
In another embodiment of the invention a surgical instrument is disclosed. The surgical instrument includes a handle, an elongated probe and at least one electrode. The elongated probe is connected to the handle. The elongated probe has a terminus distal to the handle. The electrode includes an electrode surface positioned on the terminus so that a line from a geometric center of the electrode surface and substantially perpendicular to the electrode surface intersects at an angle a longitudinal axis formed by the elongated probe. The conductor attaches the electrode to the handle.
In a further embodiment of the invention an apparatus for electrosurgical treatment of a body is disclosed. The apparatus comprises an elongated probe member having proximal and distal extremities, a handle connected to the proximal extremity and an electrode carried by the distal extremity, the probe member including a shaft having proximal and distal ends and a distal opening, the electrode including a flat plate and a cap, the plate being fixed to the distal end of the shaft and at least partially covering the distal opening, the cap enclosing the plate and a portion of the distal end of the shaft.